public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    in.nextInt();
    in.nextLine();
    String input = in.nextLine();
    LinkedList<Integer> list = new LinkedList<>();

    int count = 0;
    for (int i = 0; i < input.length(); i++) {
        char tmp = input.charAt(i);
        if (tmp == 'B') count++;
        else if (count != 0) {
            list.addLast(count);
            count = 0;
        }
    }
    if (count > 0) list.addLast(count);

    System.out.println(list.size());
    while (!list.isEmpty()) System.out.print(list.pollFirst() + " ");
}